A wellbore can have a plurality of zones. For example, a formation that contains hydrocarbons can have multiple layers that have different characteristics. A wellbore that extends through such a formation will have multiple zones that correspond to the multiple layers.
After a wellbore has been drilled through the formation, the various layers of the formation are perforated by use of perforating guns. Following perforation, testing, such as drillstem testing, is performed. Drillstem testing (DST) is a procedure to determine the productive capacity, pressure, permeability, or extent (or some combination of these characteristics) of a hydrocarbon reservoir in each layer of the formation.
In many cases, testing of multiple zones in a wellbore may be required to be performed independently. To conduct these tests, the lower layer is perforated and then DST tools are run in the hole and that layer is flow tested. The test string is then removed, and a plug is set above the tested layer and below the next layer to be tested. The next layer is then perforated and tested. This is repeated until all of the layers of interest are tested. To flow the well for production, all of the plugs will be milled out. As a result, drillstem testing of multiple zones in a wellbore can be a lengthy process that can take up to several days, which can be costly in terms of labor and equipment costs. Also, lengthy drillstem testing also delays the completion of a wellbore.